The present invention relates to testing methods and more particularly to methods for testing components having broadcast signal reception capabilities.
Because of consumer demand, the automotive industry has placed high emphasis on providing vehicles with high quality audio and reception systems. This is true not only in high end vehicles, but also in mid- to low-end vehicles. To achieve high quality sound when playing AM and FM broadcasts, it is imperative that the audio system include a high performance reception system. Without high quality signal reception, even the most advanced audio systems are incapable of providing the desired sound quality when playing AM and FM broadcasts.
Conventionally, vehicle audio systems, and particularly reception systems for vehicle audio systems, are tested or evaluated by assembling a team of individuals (xe2x80x9cratersxe2x80x9d) who ride in the vehicle and listen to the audio system as the vehicle travels a predetermined test route. The route is selected to travel through selected geographical areas where defects in the broadcast signal are likely to occur. For example, the route is selected to pass through areas where such defects as intrusion, overload, multipath and adjacent channel interference are likely to occur. By listening to the audio system throughout the test route, raters are capable of determining when various problems are present in the broadcast signal. Based on this analysis, the raters are able to provide a subjective opinion of the quality of sound produced by the audio system. To compare the quality of two different systems, the raters may travel the same route in a separate vehicle with a second system, and make comparisons between the sound and reception quality produced by the two systems.
This conventional method of testing and evaluation suffers from numerous deficiencies related to the availability and quality of raters, the comparative value of data used as the basis for assessment, and the precise timing and location of the test.
First, it is difficult to coordinate and assemble a team of raters to participate in extensive test activities, and it is even more difficult for that team to provide a high degree of experience and consistency in judgment.
Second, it is difficult for a team of raters to form a comparative assessment of alternative audio and reception systems based on the same data and using objective standards, since the assessment is necessarily instantaneous and judgmental.
Third, it is impossible to form an opinion of sound and reception quality, which is not affected by background noise such as might be caused by traffic, road conditions, weather and even conversation in the vehicle.
Finally, it is impossible for one rater to compare the quality of alternative audio or reception systems under identical broadcast conditions. The relative capabilities of such systems to provide quality output can only be accurately assessed at the precise moment of broadcast since that quality is significantly affected by broadcast content (e.g. classical music, rock music or voice), frequency modulation, weather conditions (e.g. cloudy or sunny), direction (eg north, south etc.) and location (e.g. under an overpass, through a tunnel, next to a tall building, near to power lines etc.).
The aforementioned problems are overcome by the present invention wherein a testing method is provided that permits direct comparison of audio and reception systems, and components thereof, such as antennas or radio receivers. The method generally includes the steps of: (1) providing at least two test vehicles, each equipped with a component to be tested, (2) providing each vehicle with a device for recording the output of the component to be tested, (3) providing at least one of the two vehicles with a video recording device, (4) simultaneously traveling a test route with both the vehicles remaining in close proximity, (5) recording the output signals of the components being tested as the vehicles travel the test route, (6) providing a video recording of the vehicles traveling the test route, (7) playing back at least portions of the recorded output while simultaneously playing back the corresponding portions of the recorded video, and (8) comparing the played-back portions of the recorded audio output of the components in view of the environmental conditions reflected in the played-back portions of the recorded video to provide a relative comparison of the quality of the components.
The present invention provides an effective testing method that permits greater consistency and accuracy. The system permits output generated from the same broadcast signals received at the same time and location to be directly and repeatedly compared, thereby eliminating the inherent deficiencies caused by comparing output generated by different signals at different times and locations. The system especially permits the output recordings to be analyzed by a single rater, thereby eliminating the inconsistencies resulting from differences in the subjective rating methods of different raters. The recordings can also be analyzed under lab conditions, eliminating problems caused by background noise encountered outside of the lab. Further, the video recording permits environmental conditions to be taken into account in rating the components during playback. By viewing the environmental conditions simultaneously with the recorded audio, noise and other deficiencies in the output resulting from environmental conditions can be properly assessed.
In a preferred embodiment, the recording devices are connected to the speaker output of the component being tested, such as an AM/FM receiver. This eliminates background noise as well as noise generated by the speakers or by the electrical circuit feeding the speakers.
In another preferred embodiment, the recorded signals are analyzed using a computer analysis system. The system permits the audio and video recordings to be synchronized and then analyzed under laboratory conditions. A single rater can thus test two separate systems producing sound from the same broadcast. The computer analysis system permits the recordings to be played in a variety of different modes that facilitate direct comparison of the sound recordings from the two components. For example, the system can play the same time interval of sound from both components to permit a more accurate comparison. Further, by reviewing the video recording simultaneously with the audio recording, the rater can take environmental conditions into consideration when rating the components.
The computer analysis system also provides the ability to plot the relative amplitude of the recorded audio over a range of frequencies. This permits the analyst to make a visual comparison of different audio recordings. In a preferred embodiment, the system provides the ability to plot two separate audio recordings simultaneously so that direct comparisons of the two audio recordings are possible.
In another aspect, the present invention provides a method for evaluating the quality of an audio recording. The method generally involves analyzing the level of any signals present outside the frequency range of normal sound. A particularly efficient embodiment of this method useful with FM broadcasts is to compute the difference between the relative amplitude of the FM pilot signal at 19 KHz with the relative amplitude of sound at 17 KHz. This method provides an objective rating from which to objectively compare the quality of different components. By computing the difference between the pilot signal at 19 KHz and the noise at 17 KHz, variations in the volume settings between two components can be taken into account in the rating.
These and other objects, advantages, and features of the invention will be readily understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings.